L-menthol may cause a reflex activation of upper airway muscles or a change in ventilation in sleeping healthy adults by specifically stimulating cold receptors in the airway. Eight normal adults will undergo polysomnography while wearing a face mask attached to tubing through which either room air, warm humidified room air, or warm humidified room air with L-menthol can be passed. Ventilation will be monitored with a pneumotachograph attached to the mask and electromyograms will be recorded from the alae nasi and genioglossus muscles.